brown



April 20, 1954 w. E. BROWN 2,675,707

FUSIBLE RELEASE SAFETY DEVICE FOR FURNACES AND THE LIKE Filed Oct. 2,1950 2 Sheets-Sheet l p 20, 1954 w. E. BROWN 2,675,707

FUSIBLE RELEASE SAFETY DEVICE FOR FURNACES AND THE LIKE Filed Oct. 2,1950 2 Sheets-Sheet 2 Patented Apr. 20, 1954 UNITED ENT OFFICE FUSIBLERELEASE SAFETY DEVICE FOR FURNACES AND THE LIKE William E. Brown,Pewauliee, Wis., assignor to Cutler-Hammer, 1120., Milwaukee, Wis., acorporation of Delaware 3 Claims.

This invention relates to a safety device for furnaces, boilers, spaceheaters and the like.

It is not infrequent in the operation of furnaces, boilers and spaceheaters, through malfunctioning of damper systems and fuel supplycontrol, or through neglect of the operator, that such furnaces, boilerand heaters become overheated. Such overheating greatly increases theattendant fire hazard and frequently results in serious damage to theheating system.

A primary object of the present invention is to provide a simple andnovel form of safety device which responds to attainment of excessivetemperature in furnaces, boilers and space heaters to effect immediatereduction in the rate of combustion therein.

Another object is to provide a safety device of the aforementionedcharacter which may be readily adapted to all kinds of furnaces, boilersor space heaters, and irrespective of the type of fuel or mode of fuelfeed utilized in conjunction therewith.

A further object is to provide a device of the aforementioned characterthat cannot be reset until a condition of safe operating temperatureshas been resumed, and

A still further object is to provide a safety device of theaforementioned character which may be readily reset an unlimited numberof times without the need for use of tools or replacement of parts.

Other objects and advantage of the invention will hereinafter beapparent.

The accompanying drawings illustrate a pre ferred embodiment of theinvention which will now be described, it being understood that theembodiment illustrated is susceptible of various modifications inrespect of details without departing from the scope of the appendedclaims.

In the drawings:

Figure 1 illustrates a warm air furnace together with a damper controlsystem embodying the preferred safety device;

Fig. 2 is an enlarged fragmentary view of a portion of the furnace ofFig. 1 illustrating the safety device in front elevation;

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2;

Fig. 4 schematically illustrates the use of the safety device inconnection with a furnace having motor driven fuel feeding means, and

Fig. 5 schematically illustrates the use of the safety device with aliquid or gas fired space heater.

Referring to Fig. 1, it shows a warm air furnace Hi of the hand firedtype wherein combustion is controlled by coordinated operation of acheck damper H, located in a smoke pipe 52 connecting the furnacecombustion chamber and a chimney l3, and a draft damper i i, located inthe ash pit door I5. Dampers II and M are interconnected by a chain orcable It running over guide pulley I! and I8, fixed to the ceiling oroverhead support. At one end chain I 5 is connected to damper II and atits other end it is connected to one end of a weight I? which at itsother end has connection to damper M. A chain or cable It is connectedto the end of Weight ll with which chain It is connected, passes over apulley 20 and i connected at its other end to the crank arm 2| of adamper regulator motor 22. Pulley 2!! is suspended on one end of a chainor cable 23 which passes over guide pulleys 24 and 25, fixed to theceiling or overhead support, and which is attached at its other end tothe lever arm 26 of safety device 27.

In the position of damper regulator motor 22 and damper control systemdepicted in Fig. 1, draft damper M will be open to its maximum extent,and it may be assumed that check damper II is closed to its maximumextent. With such positioning of dampers i I and It the combustion ratein furnace Ill will be at, or near, the maximum rate. If the position ofcrank arm 2| of regulator motor 22 is changed to a position oppositethat shown in Fig. 1, then the positions of dampers H and It will bereversed from that aforementioned and the minimum rate of combustion infurnace it will then be afforded.

If the air temperature inside the bonnet 28 of furnace it i maintainedbelow a predetermined safe value, then the position of pulley 20 will bemaintained fixed. However, as will be hereinafter more fully explained,if the air temperature inside the bonnet 28 should rise above suchpredetermined safe value, safety device 21 will function to effectlowering of pulley 20 to such an extent that damper M will automaticallyclose and damper M will be opened to its maximum extent, therebyproviding for minimum rate of combustion in furnace lil. Safety device27 when subjected to temperatures above a predetermined safe valueresponds to release its arm 26 for movement in the clockwise directionunder the bias of pulley 20, weight I? and damper I l. The constructionand mounting of safety device 21 in furnace it will now be described indetail.

Referring to Figs. 2 and 3, they show in greater detail safety device 21and a portion 28 of bonnet 293 immediately adjacent the safety device.

Safety device 21 comprises the aforementioned lever arm 26, a shaft 29,a tube 353, a sprin clutch 3!, a mounting plate 32, and an alloy solder33.

Mounting plate 32, which is preferably formed of cadmium plated steel oriron, is provided with a central opening to accommodate therewithin witha snug fit the tube 38. Tube 3d, which is preferably formed of brass andannular in cross section, is soldered or brazed to plate 32 for rigidconnection thereto. Shaft 29, which is preferably cylindrical in formand made of steel, is adapted to fit within the interior bore of tube 36with free clearance. Adjacent the end of shaft 29 extending within tube39, the former is provided with a portion of reduced diameter, and tube30 is circumferentially crimped, as depicted at 39 so that the innerwall thereof extends almost into engagement with such portion 2%,thereby preventing withdrawal. of shaft 29 axially of tube 36. The endof tube 39 adjacent the aforementioned end of shaft 29 is closed as bybendin the wall of the tube to a meeting relation as depicted at 36Shaft 29 is normally restrained against rotary movement relative to tube39 by the solder 33 which in hardened condition efiects a rigid bondbetween the outer surface of shaft 29 and the inner surface of tube 353.Prior to assembly, the inner surface of tube 3% and the outer surface ofshaft 29 are suitably tinned such solder, and after assembly of shaftwithin tube 36 and the aforementioned crimping and closure of the end ofthe latter additional solder is introduced between shaft 29 and tube 3dto insure a rigid connection therebetween. The composition of solder 33will vary according to the permissible maximum furnace air temperaturewhich will differ according to the size and maize of furnace and thedesign of the heating system. Generally speaking, the desired meltingpoint of solder 33 will be in the range of 250 to 450 Fahrenheit.

Shaft 29 extends outwardly beyond the open end of tube 38am appreciabledistance and carries thereon the lever arm 25 and spring clutch 3i.Lever arm 25, which is preferably a one-piece punched and stamped memberformed of cadmium plated steel or iron, comprises a flat rectangularportion 25*, triangular side portions ZG -and Et -which merge at a rightangle with portion 2% on opposite sides of the latter, and an open-eyehooked portion 25 which merges with one end of portion 26 Portions 28and 26 of arm 26 are provided with alined openings to accommodate shaft29.

Spring clutch 3!, which is preferably formed of galvanized music wire,comprises a helical coil portion 3!; an end coil portion Bi and an armportion 31. The coil turns of the portion 3 I are preferably formed sothat when free of shaft 29 the inner diameter of the coil turns will beless than the outer diameter of shaft 29. Shaft 29 is provided with aportion 25 of reduced diameter and the end coil portion 31 of clutch BIis adapted to engage said shaft thereon to restrain the clutch frommovement axially of shaft 29. The arm portion 3I of clutch 3! bearsagainst the upper surface of portion 28 of lever 25, extends downthrough an opening 25 formed in portion 25 and bears against the lowersurface of the latter portion. In the assembled relation shown in Figs.2 and 3, the coil turns of portion 3 i of the clutch tightly grip shaft29 and the portion 31 bearing against lever 26 restrains the latteragainst clockwise movement, as viewed in Figs. 1 and 2, on shaft 29.

An opening 34 formed in portion 28 of bonnet 28 is provided toaccommodate the tube 30, which tube projects into the chamber insidesaid bonnet where it is subjected to the air temperature thereprevailing. Safety device Z'l is preferably secured in mounted relationon portion 28 of bonnet 28 by stove bolts 35 penetratin receivingopenings formed in mounting plate 32 and taking into alined threadedopenings formed in portion 2%. Although not shown, a gasket formed of athermal insulating material such as asbestos may be interposed betweenmounting plate 32 and portion 28* of bonnet 28 if desired.

The operation of safety device 2? will now be described. Lever arm 26,due to the gravity bias of damper It, weight H and pulley 2b impartedthereto through the chain 23, tends to rotate in the clockwise directionon shaft 25 -iowever, as

' aforeindicated, spring clutch 3! restrains arm 2% against suchmovement, the restraint increasing with the force applied on-arm If theair temperature within bonnet 28 rises above the melting point of solder33', the latter softens and when softened sufficiently permits shaft 23to rotate freely within tube 35. Thus when solder 33 softenssufficiently the assembly comprising shaft 28, spring clutch 3| andlever arm 25 rotates clockwise under the aforementioned bias, assuming aposition such as that depicted in broken lines in Fig. 2, therebyaffording lowering of pulley 2i; and attendant closing of damper Hi andopening of damper II to reduce the combustion rate in furnace IE] to theminimumrate.

When the air temperature within bonnet 2S thereafter is reduced belowthe solidifyng point of solder 33, shaft 29 and tube 36 again becomerigidly bonded together. Safety device 27 is then in condition forresetting for further safety functioning. Resetting of the device iseffected by merely rotating lever arm 25 anticlockwise on shaft 29 tothe initial positions therefor shown in Figs. 1 and 2. As will beappreciated, when anticlockwise force is imparted on lever arm 25, thegripping force of the coil turns of portion 3 I of spring clutch 3! willbe reduced, thereby permitting anticlockwise movement of arm 2t on shaft29.

It will be apparent from the foregoing that safety device 2? can be usedrepeatedly to afford the aforedescribed safety functioning without needfor use of tools to reset or replacement of parts following safetyaction thereof.

While safety device 27 has been shown and described in conjunction witha warm air furnace, it will be apparent to those skilled in the art thatthe same can be readily adapted to afford the same type of safety actionin conjunction with hot water, vapor or steam boilers having the same orsimilar types of damper and damper control systems. When used with suchboilers. the manner of mounting safety device 2? will be different. Themost expeditious manner of mounting the same when used with boilers isto provide T fitting in the hot water, vapor or steam line leaving theboiler, providing safety device 2! with a screw thread mounting plug inplace of mounting plate 32, and screwing such plug with safety device 21mounted thereon into an opening of the T fitting. The composition of thesolder 33 of safety device 27 will vary according to the heating mediumhandled by the boiler. For use with hot water boilers the suggestedrange of melting points for solder 33 is to 208 Fahrenheit. With vaporand steam boilers the desired melting point for solder 33 will dependupon the upper limit of the working pressures of such boilers and shouldbe selected accordingly.

Safety device 21 is also adapted for use with furnaces or boilers wherefuel is fed by mechanical devices such as stokers or oil burners.Referring to Fig. 4, it schematically depicts a furnace 40, which may beassumed to be of the warm air type, and a motor driven fuel feedingdevice 4|, which may be assumed to be a motor driven stoker or oilburner. Device 4| is provided with an electric motor M having electricalsupply lines L and L which may be assumed to be connected into anydesired type of manual or automatic control system therefor. A switch42, which here is depicted for the sake of simplicity as a single poleknife switch, is connected in circuit with supply line L Safety device21 is mounted in the manner aforeindicated in the bonnet of furnace andits lever arm 26 is connected to the handle of the switch 42 by a chainor cable 43 passing over guide pulleys. A weight 44 is attached to thehandle of switch 42 and when the arm 26 of safety device 2! is releasedunder safety action of the latter, it effects opening of switch 42 tostop the motor M if the latter is then operating.

Referring to Fig. 5, it shows the use of safety device 21 in conjunctionwith a space heater 50 which may be assumed to be fed with a gaseous orliquid fuel through pipe 5| having a control valve 52. In this instancethe arrangement of safety device 21 is similar to that shown in Fig. 4,and upon safety action of device 21 a weight 53 attached to the handleof valve 52 effects closure of said valve to shut off the supply of fuelto the space heater.

I claim:

1. A thermally sensitive safety device comprising a tube for subjectionto a heat conducting medium, a shaft fitting within said tube and at oneend extending outwardly therebeyond, a lever mounted on the outwardlyextending portion of said shaft, solder bonding said shaft to the innerwall of said tube for restraining said shaft against rotary movement insaid tube whenever the temperature of the latter is below the meltingpoint of said solder, and a spring clutch disposed about said shaft andengaging with said lever to prevent rotation of the latter on said shaftin one direction while allowing unlimited rotation of said lever on saidshaft in the opposite direction, said shaft being released to permitrotary movement of the same and said lever in either direction relativeto said tube whenever the temperature of said tube exceeds the meltingpoint of said solder.

2. A thermally sensitive safety device comprising a. tube for subjectionto a heat conducting medium, a shaft fitting within said tube and at oneend extending outwardly therebeyond, solder bonding said shaft to theinner wall of said tube for restraining said shaft against movementrelative to said tube whenever the temperature of said tube is below themelting point of said solder, a lever mounted on the outwardly extendingportion of said shaft, and a spring clutch disposed about said shaft andengaging said lever for preventing rotation ofthe latter on said shaftin one direction while allowing unlimited rotation of said lever on saidshaft in the opposite direction, said shaft being released to permitunlimited rotary movement of the same and said lever in either directionrelative to said tube whenever the temperature of said tube exceeds themelting point of said solder.

3. A thermally sensitive safety device comprising a tube formed of agood heat conducting metal for subjection to a heat conducting medium, ashaft formed of metal fitting within said tube and extending at one endtherebeyond, said tube and said shaft being complementally formed toinsure against withdrawal of said shaft axially of said tube, a levermounted on the outwardly extending portion of said shaft, solder bondingsaid shaft to the inner wall of said tube for restraining said shaftagainst rotary movement in said tube whenever the temperature of the;latter is below the melting point of said solder, and a helical coilspring clutch disposed about and gripping said shaft and engaging saidlever for preventing rotation of the latter on said shaft in one'direction while allowing unlimited rotation of said lever on said shaftin the opposite direction, said shaft being released to permit unlimitedrotary movement of the same and said lever relative to said tube ineither direction whenever the temperature of said tube exceeds themelting point of said solder.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,477,027 Blanchard Dec. 11, 1923 1,688,121 Larson Oct. 16,1928 1,974,844 Cartwright Sept. 25, 1934 2,150,858 Eggleston Mar. 14,1939 2,168,749 Olds Aug. 8, 1939 2,190,892 Swepston Feb. 20, 19402,302,745 Crise Nov. 24, 1942

